Josh Obar (@obarlab.bsky.social)

Myeloid Cell States in Influenza-Associated Pulmonary Aspergillosis Are Shaped by Iron Overload and Metabolic Reprogramming Virus-associated pulmonary aspergillosis is a life-threatening secondary infection that substantially increases morbidity and mortality in critically ill patients with respiratory virus infections. Influenza A virus (IAV) and SARS-CoV2 are known to disrupt pulmonary homeostasis, the mechanisms by which these perturbations render the host susceptibility to Aspergillus fumigatus ( Af ) remain incompletely understood. Here, we integrate an established murine model of influenza-associated pulmonary aspergillosis (IAPA) with single-cell RNA sequencing (scRNA-seq) to define the myeloid cell dysfunction that underlies IAPA establishment and progression. Single-cell transcriptomic profiling of pulmonary monocytes and macrophages revealed that IAV- Af coinfection drives a marked shift away from interferon-mediated antiviral and antigen presentation programs toward stress-associated and redox-regulatory transcriptional states. Pathway analyses demonstrated coordinated suppression of phagocytic and interferon signaling pathways alongside enrichment of oxidative stress and mitochondrial metabolic signatures -- changes that closely recapitulate transcriptional defects previously reported in human IAPA patients. Myeloid cells from IAV- Af coinfected mice further exhibited increased oxidative phosphorylation alongside reduced glycolytic and phagocytic activity, consistent with impaired antifungal effector function. To elucidate how prior IAV infection generates a pulmonary microenvironment permissive to Af growth, we evaluated airway iron availability -- a critical determinant of both fungal pathogenicity and immune regulation. IAV infection alone produced a significant elevation in bronchoalveolar iron levels accompanied by induction of iron-associated inflammatory mediators. Paradoxically, during IAV- Af coinfection, myeloid cells displayed markedly reduced expression of iron-sequestering and storage genes, revealing a fundamental disconnect between iron burden and cellular iron-handling capacity. Functionally, elevated iron accelerated Af germination and impaired macrophage-mediated fungal killing. Collectively, these findings identify IAV-induced pulmonary iron accumulation as a key driver of immunometabolic reprogramming in myeloid cells, resulting in compromised antifungal immunity and heightened susceptibility to secondary Af infection. ### Competing Interest Statement The authors have declared no competing interest. National Institutes of Health, https://ror.org/01cwqze88, R21-AI152019, T32-AI007363, P20-GM130454, S10-OD025235, S10-OD030242, P30-CA023108 https://www.biorxiv.org/content/10.64898/2026.04.22.720189v1